Bio99 Practice Exam #4

1.  Genetic code

a. What amino acid(s) do the following codons code for?

i. 3’ CAU 5’

ii. 5’ CAA 3’

b. What codon(s) encode for the following amino acids? Include directionality.

i. Asp

ii. Cys

c. A tRNA has the anticodon 5’ IGA 3’. (1) What codon(s) can it bind to?  Include directionality. (2) What amino acid(s) will be attached to this tRNA?

(1)                                     (2)

d. The sequence of a given mRNA is 5’ AUGUAG 3’.  If the amino acid sequence of the protein made from this mRNA is Met-Cys-Val, this would mean the genetic code is (OVERLAPPING/NON-OVERLAPPING).

2.  Stop!

a. Which of the following best describes why splicing is important for the detection of a nonsense mutation?

A. An mRNA that is not spliced cannot be exported from the nucleus.

B. An mRNA that is not spliced will not have exon junction complex proteins associated with it.

C. An mRNA that is not spliced cannot be bound by the ribosome.

b. The Salmon gene is GFP tagged in a human tissue culture cell line.  One of the cells in the line acquires a nonsense mutation in the Salmon gene.

i. Which of the below methods would allow one to identify the presence of the nonsense mutation?  Select all that apply.

A. Northern blot

B. Western blot

C. RNA Seq

D. Immunoprecipitation

ii. For the above technique(s) that you selected, describe the experimental result that would be observed from them assuming there is a nonsense mutation.

iii. If you were detecting the nonsense mutation through the GFP tag, does it matter if the GFP gene was added at the 5’ end of the Salmon gene versus the 3’ end?

YES or NO. Which of the statements below best describes your selection.

A. As long as the promoter is unaffected, protein will still be produced.

B. Anything downstream of the nonsense mutation will not be translated.

C. Anything downstream of the nonsense mutation will not be transcribed.

D. As long as there is no mRNA splicing occurring, exon junction complexes will not impact the process.

3.  Virus!

a. Diagram the life cycle of a (+) and a (-) single stranded RNA virus.  This includes how it makes more genome and how it makes more protein.

b. TRUE or FALSE.  A bacteria can combat an RNA virus using the CRISPR system.  Which of the statements below best explains your answer?

A. CRISPR fights against foreign nucleotides.

B. CRISPR is DNA specific.

C. Guide RNA is capable of hybridizing to DNA or RNA.